Processes for the reaction of primary and secondary amines with acrylonitrile to form corresponding cyanoethylamines are well-known. Products that result from the cyanoethylation of organic amines are of industrial importance because they have broad utility in a variety of applications. For example, cyanoethylated amines can be used as coupling components in the preparation of azo dyes for paper and synthetic fibers and so forth. Also, the pendant nitrile groups can be reduced to the amine and thereby generate polyfunctional amines for use as epoxy and isocyanate curatives.
In general, amines add to acrylonitrile more easily than many organic compounds, but the ease of the addition to amines varies considerably. For example, primary amines having two active hydrogen atoms can add one or two acrylonitrile molecules. Addition of the first acrylonitrile molecule to a primary amine may occur at relatively low temperature while addition of the second acrylonitrile molecule may require heating and the use of more rigorous conditions. Stereochemistry between primary or secondary amines and the complexity of the amine also affect the rate of addition of acrylonitrile to the amine.
The following patents represent processes for the cyanoethylation of primary and secondary amines:
U.S. Pat. No. 3,231,601 discloses the cyanoethylation of aromatic amines and points out that primary and secondary aromatic amines are more difficult to cyanoethylate than their aliphatic counterparts. Cyanoethylation of the aromatic amine is effected in good yield by carrying out the reaction in an aqueous medium, i.e. water as the sole solvent, and in the presence of salts of aromatic amines and strong acids as catalysts. The patentees also point out that primary amines are more easily reacted than secondary amines and that steric hindrance of the amine group can affect reactivity, e.g., o-toluidine is less reactive than p-toluidine. Examples of strong acids suited for the catalytic reaction include sulfuric, phosphoric, hydrochloric, p-toluene sulfonic, and trifluoroacetic.
U.S. Pat. No. 3,496,213 discloses the mono-N-cyanoethylation of aromatic amines by reacting the aromatic amine with acrylonitrile in the presence of zinc chloride carried in an aqueous reaction medium. In the process one mole of acrylonitrile is reacted with one mole of monoamine.
U.S. Pat. No. 4,153,567 discloses a process for producing additives for lubricants and fuel which are based on the reaction of the acrylonitrile and vicinal cyclohexanediamine followed by reaction with a heterocyclic imide. In the process, cyanoethylation is effected by reacting 1,2 diaminocyclohexane with acrylonitrile in the presence of an acid catalyst. One and two moles of acrylonitrile are reacted with the vicinal cyclohexylamine to give both the monocyanoethylated product, i.e., N-(2-cyanoethyl)-1,2-diaminocyclohexane and the dicyanoethylated product, i.e., N,N'-di-(2-cyanoethyl)-1,2-diaminocyclohexane. Acid catalysts that may be used include p-toluene-sulfonic acid and acetic acid. Following cyanoethylation the nitrile is reduced to the amine by a catalytic hydrogenation using Raney nickel or other transition metals as catalysts.
U.S. Pat. No. 4,321,354 discloses the production of cycloaliphatic polyamines, particularly the polyamine derived from 1,2-diaminocyclohexane. As in '567, 1,2diaminocyclohexane is reacted with one or two moles acrylonitrile respectively in the presence of an acetic acid catalyst to produce N,N'-di-(2-cyanoethyl)-1,2-diaminocyclohexane. The resultant cyanoethylated diaminocyclohexanes are reduced with hydrogen to form the polyfunctional amines.